About this replacement
Fulham Hotspot 1 — 3.6V Ni-CD Replacement Battery (5600123200403.00)
This is a 3.6V, 2500mAh Ni-CD battery for the Fulham Hotspot 1 emergency lighting unit. It restores backup illumination capability when the original cell has depleted or failed. Keeping this battery serviceable is a building code compliance requirement in most jurisdictions.
- Hotspot 1 cell specification: The Fulham Hotspot 1 charge controller expects a Ni-CD cell at this exact voltage and capacity. Swapping chemistry or voltage breaks the float charge cycle — the controller will either undercharge or run a continuous trickle that damages the new cell within months.
- Bench tested on actual hardware: We ran this cell through a full mains-failure simulation. The BMS handed off cleanly to battery power, held load under the lamp draw, and the charge controller returned to green float within the expected window after mains was restored.
- First-cycle test after installation: Within 24 hours of fitting, hold the test button for the full rated duration. This confirms the cell accepts load and lets the charge controller register the new cell capacity before the next scheduled compliance inspection.
Emergency light failing its duration test after battery replacement
A fresh Ni-CD cell shipped from storage hasn't been through a conditioning cycle. On first discharge, it won't deliver rated capacity — the electrodes haven't fully formed under load. One complete charge-then-discharge cycle brings the cell up to its rated 2500mAh output. Run a full manual test within 24 hours of installation before any scheduled compliance test. After that cycle, the cell will meet the duration requirement at 3.6V under rated lamp load.
Charge indicator staying red after new battery installation
If the Hotspot 1's charge LED stays red after fitting the new cell, the controller is seeing a resting voltage outside its float acceptance window. Ni-CD cells can sit at a suppressed open-circuit voltage after extended storage. Leave the unit on mains power for a full charge cycle — typically 24 hours — without triggering the test button. If the LED hasn't shifted to green after 24 hours, check the connector seating and confirm polarity; a reversed connection will hold the cell at zero charge indefinitely.